Python Regex matching and replacing

I have a pdf file with its contents formatted as follows:

00:12 There once lived a man...

00:18 who was thought to have...

and the list goes on following the same pattern. Now I'm trying to write a Regex program that will read the file and remove all of the time stamps as well as replace the line skips with spaces. In other words. I want to make one big paragraph out of it.

This is what I came up for the reg expression:

transcript.replace(transcript.matches("^[0-9:]+$"),"")

and that will get rid of any numbers and colons, meaning the time stamps. Now I'm not sure how to replace the line skips, would I do something like